The present invention relates to an electric steering lock apparatus, and more particularly, to an electric steering lock apparatus that protects an incorporated actuator from being overheated.
Mechanical steering lock apparatuses have conventionally been used to prevent vehicles from being stolen.
Japanese Laid-Open Patent Publication No. 11-105673 describes a mechanical steering lock apparatus having a key cylinder. A mechanical key is inserted in the key cylinder and turned to move a lock pin, which is engaged with and disengaged from a steering shaft. The engagement of the lock pin with the steering shaft locks the steering shaft and restricts the rotation of the steering wheel. The rotation restriction improves the security of the vehicle with respect to automobile thefts.
In recent years, to improve the maneuverability of a vehicle, a one-push type engine start/stop system having a button switch for starting and stopping an engine has been proposed. In a steering lock apparatus (electric steering lock apparatus) for such a start/stop system, an actuator moves a lock pin that is engaged with and disengaged from the steering shaft. A lock control unit controls the actuator.
In the electric steering lock apparatus of the prior art, frequent locking and unlocking of the steering shaft may overheat the actuator (motor) and cause thermal damage, such as line breakage of a coil. A motor provided with an overheat protection function may be employed to prevent such thermal damage. However, such a motor provided with an overheat protection function would have a bimetallic hardware structure. This would increase the size and cost of the motor. Accordingly, the employment of a motor provided with an overheat protection function would enlarge the steering lock apparatus and increase the manufacturing cost.